Hydrogen peroxide (H2O2) is an important analyte in many fields, such as food, pharmaceuticals, chemical, clinical, printing, and environments, while also being a byproduct in various enzymatic reactions of many peroxidase enzymes, such as glucose oxidase and lactate oxidase. H2O2 is extremely toxic to living organisms. Therefore, development of simple, sensitive, inexpensive, disposable and accurate sensors for H2O2 detection is very important.
Electrochemical methods of sensing H2O2 have attracted much attention due to their simplicity, sensitivity and portability. However, conventional electrodes showed poor electrocatalytic properties towards the electrochemical reaction of H2O2. As a result, many sensitive hydrogen peroxide enzyme-based sensors (e.g. HRP-, myoglobin-, cytochrome C-modified electrodes) were developed with high catalytic properties. Nevertheless, due to complicated enzyme immobilization procedures, instability, and the high cost of the enzyme and/or expensive substrates, the use of enzyme-modified electrodes for the detection of H2O2 has its limitations.
Nanomaterials that have high electrocatalytic properties, a high surface-to-volume ratio, high stability, and low cost are being used on various electrode surface modifications. For instance, palladium nanoparticles (PdNPs) embedded into a hierarchically porous TiO2 hollow spheres-modified glassy carbon electrode (GCE), a multi-walled carbon nanotube-PdNPs-modified GCE, a multi-walled carbon nanotube-PtNPs-modified GCE, a carbon nanotube-wired CuO nanoflower-modified GCE, a composite of carbon nanotube and silver NP-modified carbon ceramic electrode, a gold NP-modified indium-tin oxide electrode, and silver NP-modified carbon ion liquid electrode have been applied for the electrochemical detection of H2O2.
Platinum, gold, and glassy carbon conventional electrodes are expensive and show high background currents, unlike the graphite pencil electrode (GPE), which has a renewable surface and low cost, and which gives a relatively low background current. However, due to the poor electrocatalytic properties of the GPE towards the electrochemical reaction of many electroactive molecules, the modification of GPE with a particular electrocatalyst is required for fabricating a sensitive sensor. A PdNP-modified electrode exhibits good electrocatalytic properties for a large number of electroactive molecules, such as catecholamine neurotransmitters, methanol, formic acid and hydrogen peroxide.
Thus, a disposable palladium nanoparticle-modified graphite pencil electrode solving the aforementioned problems is desired.